An image processing pipeline (IPP) commonly refers to a sequence of operations applied to an image, and the pipeline can start at the image source (e.g., a camera) and end at the image renderer (e.g., a television). The image data often undergoes manipulations which require one or more non-linear conversions between spaces. FIG. 1A shows an example of an image processing pipeline which includes such a conversion. In the pipeline of FIG. 1A, an input 10 containing image data in a general intermediate color space (denoted as color space ABC) is provided as an input to the converter 12 which uses a non-linear function H0 to convert image data in the ABC color space to image data 14 in another color space, denoted as color space JKL, which can be an RGB-type color space. The image data 14 can be further processed (e.g., in operations 16), resulting in an input 19 (in the RGB linear light color space—RGBL) that is provided to a transfer function 21 which is the electro-optical transfer function (EOTF) of the target display. The TEOTF (Target Electro-Optical Transfer Function) 21 produces an output 23 that can drive the target display. The non-linear function H0 and potentially other functions not shown (in operations 16), such as perceptual quantization (PQ) functions, can be very complex non-linear functions.
As used herein “IPT color space” refers to a Luma (I)-Chroma (P and T)-like space (like YCbCr). The original IPT space was described in “Development and testing of a color space (ipt) with improved hue uniformity”, by F. Ebner and M. D. Fairchild, in Proc. 6th Color Imaging Conference: Color Science, Systems, and Applications, IS&T, Scottsdale, Ariz., November 1998, pp. 8-13 (to be referred to as the Ebner paper), which is incorporated herein by reference in its entirety. More recently, the final non-linearity in the Ebner paper was replaced by a perceptual quantizer (PQ) that better matches the properties of the human visual system. The PQ quantizer is described in U.S. Pat. No. 9,077,994, by J. S. Miller et al., which is incorporated herein by reference in its entirety, parts of which have been adopted by the SMPTE ST 2084:2014 specification, titled “High Dynamic Range Electro-optical Transfer Function of Mastering Reference Displays,” Aug. 16, 2014, incorporated herein by reference in its entirety. In certain embodiments, IPT may refer to the ICtCp color space defined in the ITU-R Rec. BT. 2100-0 (July 2016), “Image parameter values for high dynamic range television for use in production and international programme exchange,” which is incorporated herein by reference in its entirety. Like YCbCr, ICtCp is a color-opponent based encoding scheme intended to separate luma from chroma information. In addition, ICtCp offers constant intensity (CI) representation.